Dental implants are routinely used to replace missing teeth in both the maxilla and mandible jawbones. These implants are restored with crowns and/or bridges. The choice and design depend upon the number of teeth missing and the location of the implants. The single crown typically consists of a metal framework veneered with porcelain. Smaller bridges are also made from metal and porcelain while the larger prostheses consist of a metal framework or substructure and an acrylic resin denture tooth supra-structure. For crowns and all bridges, the metal framework incorporates machined gold alloy components called cylinders. The cylinders allow the metal framework to be connected to the abutments which are in turn connected to the implants. The periodontal ligament is a soft tissue membrane located in the mouth between tooth and bone and absorbs energy during the chewing process. Dental implants are fused to bone and, as noted above, are typically fabricated of a metal superstructure which lacks resilience characteristic of the periodontal ligament. This results in higher stresses to implants and the dental prosthesis. Further, the metal framework is cast and does not typically fit onto the abutments well. Thus, it must often be cut and refitted and the pieces are then soldered together. The process is time consuming and the materials used to fabricate the framework and abutments (e.g., gold) can be expensive. Additionally, it may be difficult to completely cover the metal framework which results in a less aesthetic appearance.
Carbon/graphite reinforced autopolymerizing poly(methyl methacrylate) bridges and frameworks were attempted heretofore but were found insufficient due to the procedures and designs used to fabricate the bridges and frameworks. Retention of the materials was found inadequate and fractures were found to occur in the final prosthesis. Bergendal et al., 1995 Clin Oral Imp Res, reported limited success in a clinical trial using carbon/graphite fiber reinforced PMMA for the fabrication of a framework in an implant system. Fractures occurred in the framework adjacent the end abutment propagating through the acrylic resin and carbon/graphite fibers to the gold and/or titanium cylinders. The cylinders were not designed to provide adequate retention of the framework materials. Additionally, fracture sites in connection with cylinders showed incomplete wetting of the fibers with polymer.
It is desirable to provide an implant system which is able to provide adequate retention of fiber reinforced composite material and to reduce and/or prevent fracture of the prostheses made therefrom. It is advantageous to provide an implant system having good esthetics and adaptability.